The technology always gets developed with which we find no exception for the printer which is evolved from the dot-matrix one to the inkjet one, and further to the laser one. As the inkjet one is more economical than the laser one, the inkjet printer still plays an important role in nowaday market. The primary working principle of an inkjet printer is to control the jetting of fine vaporized ink-drops by vaporizing the ink through an electrical heating or by piezoelectrically extruding the ink. So far as the ink cartridge of the electrical heating type is concerned, there is provided with a heating plate being a resistor layer having a flat surface and protected by growing thereon a combined structure of ceramic layer and tough metal layer from being easily cracked. It is, however, imaginable that when the ink unsuccessfully jetted out of the ink-jetting holes backwardly impacts upon the combined structure and the resistor layer, they will be subject to continuous shock waves and apt to crack which will end the use life of the inkjet. It is therefore tried by the applicant to deal with the above situation encountered by the prior art.